Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification

Sankar, A.; Ayyangar, Komanduri M.; Nehru, R. Mothilal; Gopalakrishna Kurup, P.G.; Murali, V.; Enke, Charles A.; Velmurugan, J.

doi:10.1016/j.meddos.2006.06.001

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Volume 31, Issue 4 , Pages 273-282, Winter 2006

Comparison of Kodak EDR2 and Gafchromic EBT film for intensity-modulated radiation therapy dose distribution verification

A. Sankar, M.Sc
- Department of Radiation Oncology, Apollo Specialty Hospital, Chennai, India
- Department of Physics, Anna University, Chennai, India
- Reprint requests to: A. Sankar, Department of Radiation Oncology, Apollo Specialty Hospital, 320 Mount Road, Chennai-600 035, India
Komanduri M. Ayyangar, Ph.D
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA
R. Mothilal Nehru, Ph.D
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA
P.G. Gopalakrishna Kurup, Ph.D
- Department of Radiation Oncology, Apollo Specialty Hospital, Chennai, India
V. Murali, Ph.D
- Department of Radiation Oncology, Apollo Specialty Hospital, Chennai, India
Charles A. Enke, M.D.
- Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, USA
J. Velmurugan
- Department of Physics, Anna University, Chennai, India

Received 5 October 2005; accepted 2 June 2006.

Abstract

The quantitative dose validation of intensity-modulated radiation therapy (IMRT) plans require 2-dimensional (2D) high-resolution dosimetry systems with uniform response over its sensitive region. The present work deals with clinical use of commercially available self-developing Radio Chromic Film, Gafchromic EBT film, for IMRT dose verification. Dose response curves were generated for the films using a VXR-16 film scanner. The results obtained with EBT films were compared with the results of Kodak extended dose range 2 (EDR2) films. The EBT film had a linear response between the dose range of 0 to 600 cGy. The dose-related characteristics of the EBT film, such as post irradiation color growth with time, film uniformity, and effect of scanning orientation, were studied. There was up to 8.6% increase in the color density between 2 to 40 hours after irradiation. There was a considerable variation, up to 8.5%, in the film uniformity over its sensitive region. The quantitative differences between calculated and measured dose distributions were analyzed using DTA and Gamma index with the tolerance of 3% dose difference and 3-mm distance agreement. The EDR2 films showed consistent results with the calculated dose distributions, whereas the results obtained using EBT were inconsistent. The variation in the film uniformity limits the use of EBT film for conventional large-field IMRT verification. For IMRT of smaller field sizes (4.5 × 4.5 cm), the results obtained with EBT were comparable with results of EDR2 films.

Key Words: Intensity-modulated radiation therapy, Radiochromic films, EDR2, Gamma